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Dal Cortivo G, Marino V, Iacobucci C, Vallone R, Arlt C, Rehkamp A, Sinz A, Dell'Orco D. Oligomeric state, hydrodynamic properties and target recognition of human Calcium and Integrin Binding protein 2 (CIB2). Sci Rep 2019; 9:15058. [PMID: 31636333 PMCID: PMC6803640 DOI: 10.1038/s41598-019-51573-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Accepted: 09/12/2019] [Indexed: 11/23/2022] Open
Abstract
Calcium- and Integrin-Binding protein 2 (CIB2) is a small and ubiquitously expressed protein with largely unknown biological function but ascertained role in hearing physiology and disease. Recent studies found that CIB2 binds Ca2+ with moderate affinity and dimerizes under conditions mimicking the physiological ones. Here we provided new lines of evidence on CIB2 oligomeric state and the mechanism of interaction with the α7B integrin target. Based on a combination of native mass spectrometry, chemical cross-linking/mass spectrometry, analytical gel filtration, dynamic light scattering and molecular dynamics simulations we conclude that CIB2 is monomeric under all tested conditions and presents uncommon hydrodynamic properties, most likely due to the high content of hydrophobic solvent accessible surface. Surface plasmon resonance shows that the interaction with α7B occurs with relatively low affinity and is limited to the cytosolic region proximal to the membrane, being kinetically favored in the presence of physiological Mg2+ and in the absence of Ca2+. Although CIB2 binds to an α7B peptide in a 1:1 stoichiometry, the formation of the complex might induce binding of another CIB2 molecule.
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Affiliation(s)
- Giuditta Dal Cortivo
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy
| | - Valerio Marino
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy
- Department of Translational Research and New Technologies in Medicine and Surgery, University of Pisa, Pisa, Italy
| | - Claudio Iacobucci
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Rosario Vallone
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy
- Structural Biology and Biophysics Unit, Fondazione Ri.MED, Palermo, Italy
| | - Christian Arlt
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Anne Rehkamp
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Andrea Sinz
- Department of Pharmaceutical Chemistry and Bioanalytics, Institute of Pharmacy, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Daniele Dell'Orco
- Department of Neurosciences, Biomedicine and Movement Sciences, Section of Biological Chemistry, University of Verona, Verona, Italy.
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2
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Pagani G, Gohlke H. On the contributing role of the transmembrane domain for subunit-specific sensitivity of integrin activation. Sci Rep 2018; 8:5733. [PMID: 29636500 PMCID: PMC5893634 DOI: 10.1038/s41598-018-23778-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Accepted: 03/20/2018] [Indexed: 12/20/2022] Open
Abstract
Integrins are α/β heterodimeric transmembrane adhesion receptors. Evidence exists that their transmembrane domain (TMD) separates upon activation. Subunit-specific differences in activation sensitivity of integrins were reported. However, whether sequence variations in the TMD lead to differential TMD association has remained elusive. Here, we show by molecular dynamics simulations and association free energy calculations on TMDs of integrin αIIbβ3, αvβ3, and α5β1 that αIIbβ3 TMD is most stably associated; this difference is related to interaction differences across the TMDs. The order of TMD association stability is paralleled by the basal activity of these integrins, which suggests that TMD differences can have a decisive effect on integrin conformational free energies. We also identified a specific order of clasp disintegration upon TMD dissociation, which suggests that the closed state of integrins may comprise several microstates. Our results provide unprecedented insights into a possibly contributing role of TMD towards subunit-specific sensitivity of integrin activation.
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Affiliation(s)
- Giulia Pagani
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich-Heine-Universität Düsseldorf, 40225, Düsseldorf, Germany
| | - Holger Gohlke
- Institute of Pharmaceutical and Medicinal Chemistry, Heinrich-Heine-Universität Düsseldorf, 40225, Düsseldorf, Germany.
- John von Neumann Institute for Computing (NIC), Jülich Supercomputing Centre (JSC) & Institute for Complex Systems - Structural Biochemistry (ICS 6), Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
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3
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Donnelly SK, Cabrera R, Mao SPH, Christin JR, Wu B, Guo W, Bravo-Cordero JJ, Condeelis JS, Segall JE, Hodgson L. Rac3 regulates breast cancer invasion and metastasis by controlling adhesion and matrix degradation. J Cell Biol 2017; 216:4331-4349. [PMID: 29061650 PMCID: PMC5716284 DOI: 10.1083/jcb.201704048] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 07/28/2017] [Accepted: 09/25/2017] [Indexed: 01/21/2023] Open
Abstract
The initial step of metastasis is the local invasion of tumor cells into the surrounding tissue. Invadopodia are actin-based protrusions that mediate the matrix degradation necessary for invasion and metastasis of tumor cells. We demonstrate that Rac3 GTPase is critical for integrating the adhesion of invadopodia to the extracellular matrix (ECM) with their ability to degrade the ECM in breast tumor cells. We identify two pathways at invadopodia important for integrin activation and delivery of matrix metalloproteinases: through the upstream recruiter CIB1 as well as the downstream effector GIT1. Rac3 activity, at and surrounding invadopodia, is controlled by Vav2 and βPIX. These guanine nucleotide exchange factors regulate the spatiotemporal dynamics of Rac3 activity, impacting GIT1 localization. Moreover, the GTPase-activating function of GIT1 toward the vesicular trafficking regulator Arf6 GTPase is required for matrix degradation. Importantly, Rac3 regulates the ability of tumor cells to metastasize in vivo. The Rac3-dependent mechanisms we show in this study are critical for balancing proteolytic activity and adhesive activity to achieve a maximally invasive phenotype.
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Affiliation(s)
- Sara K Donnelly
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY.,Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY
| | - Ramon Cabrera
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY
| | - Serena P H Mao
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY
| | - John R Christin
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY
| | - Bin Wu
- Biophysics and Biophysical Chemistry, School of Medicine, Johns Hopkins University, Baltimore, MD
| | - Wenjun Guo
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY
| | - Jose Javier Bravo-Cordero
- Department of Medicine, Division of Hematology and Medical Oncology, Icahn School of Medicine, Tisch Cancer Institute at Mount Sinai, New York, NY
| | - John S Condeelis
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY.,Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY
| | - Jeffrey E Segall
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY.,Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY
| | - Louis Hodgson
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY .,Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY
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Naik MU, Naik TU, Summer R, Naik UP. Binding of CIB1 to the αIIb tail of αIIbβ3 is required for FAK recruitment and activation in platelets. PLoS One 2017; 12:e0176602. [PMID: 28542214 PMCID: PMC5443481 DOI: 10.1371/journal.pone.0176602] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 04/13/2017] [Indexed: 12/03/2022] Open
Abstract
Background It is believed that activation of c-Src bound to the integrin β3 subunit initiates outside-in signaling. The involvement of αIIb in outside-in signaling is poorly understood. Objectives We have previously shown that CIB1 specifically interacts with the cytoplasmic domain of αIIb and is required for αIIbβ3 outside-in signaling. Here we evaluated the role of CIB1 in regulating outside-in signaling in the absence of inside-out signaling. Methods We used αIIb cytoplasmic domain peptide and CIB1-function blocking antibody to inhibit interaction of CIB1 with αIIb subunit as well as Cib1-/- platelets to evaluate the consequence of CIB1 interaction with αIIb on outside-in signaling. Results Fibrinogen binding to αIIbβ3 results in calcium-dependent interaction of CIB1 with αIIb, which is not required for filopodia formation. Dynamic rearrangement of cytoskeleton results in CIB1-dependent recruitment of FAK to the αIIb complex and its activation. Disruption of the association of CIB1 and αIIb by incorporation of αIIb peptide or anti-CIB1 inhibited both FAK association and activation. Furthermore, FAK recruitment to the integrin complex was required for c-Src activation. Inhibition of c-Src had no effect on CIB1 accumulation with the integrin at the filopodia, suggesting that c-Src activity is not required for the formation of CIB1-αIIb-FAK complex. Conclusion Our results suggest that interaction of CIB1 with αIIb is one of the early events occurring during outside-in signaling. Furthermore, CIB1 recruits FAK to the αIIbβ3 complex at the filopodia where FAK is activated, which in turn activates c-Src, resulting in propagation of outside-in signaling leading to platelet spreading.
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Affiliation(s)
- Meghna U. Naik
- Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA, United States of America
| | - Tejal U. Naik
- Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA, United States of America
| | - Ross Summer
- Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA, United States of America
| | - Ulhas P. Naik
- Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA, United States of America
- * E-mail:
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Duarte CEM, Abranches MV, Silva PF, de Paula SO, Cardoso SA, Oliveira LL. A new TRAF-like protein from B. oleracea ssp. botrytis with lectin activity and its effect on macrophages. Int J Biol Macromol 2016; 94:508-514. [PMID: 27771409 DOI: 10.1016/j.ijbiomac.2016.10.061] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2016] [Revised: 10/16/2016] [Accepted: 10/18/2016] [Indexed: 10/20/2022]
Abstract
Lectins are involved in a wide range of biological mechanisms, like immunomodulatory agent able to activate the innate immunity. In this study, we purified and characterized a new lectin from cauliflower (Brassica oleracea ssp. botrytis - BOL) by three sequential chromatographic steps and confirmed the purity by SDS-PAGE. Additionally, we evaluated the role of the lectin in innate immunity by a phagocytosis assay, production of H2O2 and NO. BOL was characterized like a non-glycosylated protein that showed a molecular mass of ∼34kDa in SDS-PAGE. Its N-terminal sequence (ETRAFREERPSSKIVTIAG) did not reveal any similarity to the other lectins; nevertheless, it showed 100% homology to a putative TRAF-like protein from Brassica rapa and Brassica napus. This is a first report of the TRAF-protein with lectinic activity. The BOL retained its complete hemagglutination activity from 4°C up to 60°C, with stability being more apparent between pH 7.0 and 8.0. Moreover, the lectin was able to stimulate phagocytosis and induce the production of H2O2 and NO. Therefore, BOL can be explored as an immunomodulatory agent by being able to activate the innate immunity and favor antigen removal.
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Affiliation(s)
- Christiane E M Duarte
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, MG, Brazil
| | - Monise V Abranches
- Departamento de Nutrição e Saúde, Universidade Federal de Viçosa, 38810-000 Rio Paranaíba, MG, Brazil
| | - Patrick F Silva
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, MG, Brazil
| | - Sérgio O de Paula
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, MG, Brazil
| | - Silvia A Cardoso
- Departamento de Medicina e Enfermagem, Universidade Federal de Viçosa, 36570-900 Viçosa, MG, Brazil
| | - Leandro L Oliveira
- Departamento de Biologia Geral, Universidade Federal de Viçosa, 36570-900 Viçosa, MG, Brazil.
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Leisner TM, Freeman TC, Black JL, Parise LV. CIB1: a small protein with big ambitions. FASEB J 2016; 30:2640-50. [PMID: 27118676 DOI: 10.1096/fj.201500073r] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 04/05/2016] [Indexed: 12/11/2022]
Abstract
Calcium- and integrin-binding protein 1 (CIB1) is a small, ubiquitously expressed protein that was first identified as an intracellular binding partner of a platelet-specific α-integrin cytoplasmic tail. Although early studies revealed a role for CIB1 in regulating platelet integrin activity, recent studies have indicated a more diverse role for CIB1 in many different cell types and processes, including calcium signaling, migration, adhesion, proliferation, and survival. Increasing evidence also points to a novel role for CIB1 in cancer and cardiovascular disease. In addition, an array of CIB1 binding partners has been identified that provide important insight into how CIB1 may regulate these processes. Some of these binding partners include the serine/threonine kinases, p21-activated kinase 1 (PAK1), apoptosis signal-regulating kinase 1 (ASK1), and polo-like kinase 3 (PLK3). Structural and mutational studies indicate that CIB1 binds most or all of its partners via a well-defined hydrophobic cleft. Although CIB1 itself lacks known enzymatic activity, it supports the PI3K/AKT and MEK/ERK oncogenic signaling pathways, in part, by directly modulating enzymes in these pathways. In this review, we discuss our current understanding of CIB1 and key questions regarding structure and function and how this seemingly diminutive protein impacts important signaling pathways and cellular processes in human health and disease.-Leisner, T. M., Freeman, T. C., Black, J. L., Parise, L. V. CIB1: a small protein with big ambitions.
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Affiliation(s)
- Tina M Leisner
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Thomas C Freeman
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Justin L Black
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA
| | - Leslie V Parise
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina, USA; McAllister Heart Institute, University of North Carolina, Chapel Hill, North Carolina, USA; and Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina, USA
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7
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Freeman TC, Black JL, Bray HG, Dagliyan O, Wu YI, Tripathy A, Dokholyan NV, Leisner TM, Parise LV. Identification of novel integrin binding partners for calcium and integrin binding protein 1 (CIB1): structural and thermodynamic basis of CIB1 promiscuity. Biochemistry 2013; 52:7082-90. [PMID: 24011356 DOI: 10.1021/bi400678y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The short cytoplasmic tails of the α- and β-chains of integrin adhesion receptors regulate integrin activation and cell signaling. Significantly less is known about proteins that bind to α-integrin cytoplasmic tails (CTs) as opposed to β-CTs to regulate integrins. Calcium and integrin binding protein 1 (CIB1) was previously identified as an αIIb binding partner that inhibits agonist-induced activation of the platelet-specific integrin, αIIbβ3. A sequence alignment of all α-integrin CTs revealed that key residues in the CIB1 binding site of αIIb are well-conserved, and was used to delineate a consensus binding site (I/L-x-x-x-L/M-W/Y-K-x-G-F-F). Because the CIB1 binding site of αIIb is conserved in all α-integrins and CIB1 expression is ubiquitous, we asked if CIB1 could interact with other α-integrin CTs. We predicted that multiple α-integrin CTs were capable of binding to the same hydrophobic binding pocket on CIB1 with docking models generated by all-atom replica exchange discrete molecular dynamics. After demonstrating novel in vivo interactions between CIB1 and other whole integrin complexes with co-immunoprecipitations, we validated the modeled predictions with solid-phase competitive binding assays, which showed that other α-integrin CTs compete with the αIIb CT for binding to CIB1 in vitro. Isothermal titration calorimetry measurements indicated that this binding is driven by hydrophobic interactions and depends on residues in the CIB1 consensus binding site. These new mechanistic details of CIB1-integrin binding imply that CIB1 could bind to all integrin complexes and act as a broad regulator of integrin function.
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Affiliation(s)
- Thomas C Freeman
- Department of Biochemistry and Biophysics, ‡Lineberger Comprehensive Cancer Center, and §McAllister Heart Institute, School of Medicine, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States
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Surya W, Li Y, Millet O, Diercks T, Torres J. Transmembrane and Juxtamembrane Structure of αL Integrin in Bicelles. PLoS One 2013; 8:e74281. [PMID: 24069290 PMCID: PMC3771934 DOI: 10.1371/journal.pone.0074281] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 07/30/2013] [Indexed: 12/28/2022] Open
Abstract
The accepted model for the interaction of α and β integrins in the transmembrane (TM) domain is based on the pair αIIbβ3. This involves the so-called outer and inner membrane association clasps (OMC and IMC, respectively). In the α chain, the OMC involves a GxxxG-like motif, whereas in the IMC a conserved juxtamembrane GFFKR motif experiences a backbone reversal that partially fills the void generated by TM separation towards the cytoplasmic half. However, the GFFKR motif of several α integrin cytoplasmic tails in non-bicelle environments has been shown to adopt an α-helical structure that is not membrane-embedded and which was shown to bind a variety of cytoplasmic proteins. Thus it is not known if a membrane-embedded backbone reversal is a conserved structural feature in α integrins. We have studied the system αLβ2 because of its importance in leukocytes, where integrin deactivation is particularly important. Herein we show that the backbone reversal feature is not only present in αIIb but also in αL-TM when reconstituted in bicelles. Additionally, titration with β2 TM showed eight residues clustering along one side of αL-TM, forming a plausible interacting face with β2. The latter orientation is consistent with a previously predicted reported polar interaction between αL Ser-1071 and β2 Thr-686.
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Affiliation(s)
- Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Yan Li
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Oscar Millet
- Structural Biology Unit, CIC BioGUNE, Derio Vizcaya, Spain
| | - Tammo Diercks
- Structural Biology Unit, CIC BioGUNE, Derio Vizcaya, Spain
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- * E-mail:
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Chua GL, Tang XY, Patra AT, Tan SM, Bhattacharjya S. Structure and binding interface of the cytosolic tails of αXβ2 integrin. PLoS One 2012; 7:e41924. [PMID: 22844534 PMCID: PMC3406025 DOI: 10.1371/journal.pone.0041924] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 06/26/2012] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Integrins are signal transducer proteins involved in a number of vital physiological processes including cell adhesion, proliferation and migration. Integrin molecules are hetero-dimers composed of two distinct subunits, α and β. In humans, 18 α and 8 β subunits are combined into 24 different integrin molecules. Each of the subunit comprises a large extracellular domain, a single pass transmembrane segment and a cytosolic tail (CT). The CTs of integrins are vital for bidirectional signal transduction and in maintaining the resting state of the receptors. A large number of intracellular proteins have been found to interact with the CTs of integrins linking integrins to the cytoskeleton. METHODOLOGY/PRINCIPAL FINDINGS In this work, we have investigated structure and interactions of CTs of the leukocyte specific integrin αXβ2. We determined the atomic resolution structure of a myristoylated CT of αX in perdeuterated dodecylphosphocholine (DPC) by NMR spectroscopy. Our results reveal that the 35-residue long CT of αX adopts an α-helical conformation for residues F4-N17 at the N-terminal region. The remaining residues located at the C-terminal segment of αX delineate a long loop of irregular conformations. A segment of the loop maintains packing interactions with the helical structure by an extended non-polar surface of the αX CT. Interactions between αX and β2 CTs are demonstrated by (15)N-(1)H HSQC NMR experiments. We find that residues constituting the polar face of the helical conformation of αX are involved in interactions with the N-terminal residues of β2 CT. A docked structure of the CT complex indicates that a network of polar and/or salt-bridge interactions may sustain the heteromeric interactions. CONCLUSIONS/SIGNIFICANCE The current study provides important insights into the conservation of interactions and structures among different CTs of integrins.
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Affiliation(s)
- Geok-Lin Chua
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Xiao-Yan Tang
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Alok Tanala Patra
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Suet-Mien Tan
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Surajit Bhattacharjya
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
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West XZ, Meller N, Malinin NL, Deshmukh L, Meller J, Mahabeleshwar GH, Weber ME, Kerr BA, Vinogradova O, Byzova TV. Integrin β3 crosstalk with VEGFR accommodating tyrosine phosphorylation as a regulatory switch. PLoS One 2012; 7:e31071. [PMID: 22363548 PMCID: PMC3281915 DOI: 10.1371/journal.pone.0031071] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 01/01/2012] [Indexed: 02/05/2023] Open
Abstract
Integrins mediate cell adhesion, migration, and survival by connecting intracellular machinery with the surrounding extracellular matrix. Previous studies demonstrated the importance of the interaction between β3 integrin and VEGF type 2 receptor (VEGFR2) in VEGF-induced angiogenesis. Here we present in vitro evidence of the direct association between the cytoplasmic tails (CTs) of β3 and VEGFR2. Specifically, the membrane-proximal motif around 801YLSI in VEGFR2 mediates its binding to non-phosphorylated β3CT, accommodating an α-helical turn in integrin bound conformation. We also show that Y747 phosphorylation of β3 enhances the above interaction. To demonstrate the importance of β3 phosphorylation in endothelial cell functions, we synthesized β3CT-mimicking Y747 phosphorylated and unphosphorylated membrane permeable peptides. We show that a peptide containing phospho-Y747 but not F747 significantly inhibits VEGF-induced signaling and angiogenesis. Moreover, phospho-Y747 peptide exhibits inhibitory effect only in WT but not in β3 integrin knock-out or β3 integrin knock-in cells expressing β3 with two tyrosines substituted for phenylalanines, demonstrating its specificity. Importantly, these peptides have no effect on fibroblast growth factor receptor signaling. Collectively these data provide novel mechanistic insights into phosphorylation dependent cross-talk between integrin and VEGFR2.
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Affiliation(s)
- Xiaoxia Z. West
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Nahum Meller
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Nikolay L. Malinin
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Lalit Deshmukh
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Connecticut, Storrs, Connecticut, United States of America
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Julia Meller
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Ganapati H. Mahabeleshwar
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- University Hospitals Harrington-McLaughlin Heart & Vascular Institute and Case Cardiovascular Research Institute, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
| | - Malory E. Weber
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Bethany A. Kerr
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Olga Vinogradova
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Connecticut, Storrs, Connecticut, United States of America
- * E-mail: (OV); (TVB)
| | - Tatiana V. Byzova
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- * E-mail: (OV); (TVB)
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Yamodo IH, Blystone SD. Calcium Integrin Binding Protein Associates with Integrins α Vβ 3 and α IIbβ 3 Independent of β 3 Activation Motifs. ACTA ACUST UNITED AC 2012; 1:30-37. [PMID: 24163826 DOI: 10.4236/cellbio.2012.12004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Calcium Integrin Binding protein (CIB) has been identified as interacting specifically with the cytoplasmic tail of the integrin αIIb domain to induce receptor activation and integrin αIIbβ3 mediated cell adhesion to extracellular proteins. In K562 cells stably expressing mutated integrin αVβ3, or chimeric αVβ3 carrying αIIb cytoplasmic tail, we report that the interaction of CIB with β3 integrins is not αIIbβ3 specific but binds αIIb as well as αV cytoplasmic tail domains. A double mutation of two proline residues to alanine residues in the αIIb cytoplasmic domain, previously shown to disturb its conformation, inhibits chimeric αV/αIIbβ3-CIB interaction. This demonstrates that αIIb cytoplasmic domain loop-like conformation is required for interaction with CIB. Moreover, mutations of β3 cytoplasmic domain residues Tyr-747 and/or Tyr-759 to phenylalanine residues (Y747F, Y759F, and Y747,759F) as well as residues Ser-752 to proline or alanine (S752P and S752A), do not affect the αIIbβ3 or αVβ3 interaction with CIB. Since tyrosine residues Tyr-747 and/or Tyr-759 are the sites of tyrosine phosphorylation of β3 subunit, these results suggest that the β3 integrin-CIB interaction occurs through a β3-phosphorylation independent mechanism. Likewise, ablation of conformation-dependent affinity change in β3 Ser752Pro mutation had no affect on CIB-β3 interaction. In summary, our results demonstrate that the αIIb-subunit integrin and CIB interaction is non-exclusive and requires the loop-like αIIb-cytoplasmic domain conformation. An interaction of CIB with αV-containing integrins provides an additional role for this molecule in keeping with its expression outside of platelets.
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Affiliation(s)
- Innocent H Yamodo
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, USA
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Chua GL, Tang XY, Amalraj M, Tan SM, Bhattacharjya S. Structures and interaction analyses of integrin αMβ2 cytoplasmic tails. J Biol Chem 2011; 286:43842-43854. [PMID: 22052909 DOI: 10.1074/jbc.m111.280164] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Integrins are heterodimeric (α and β subunits) signal transducer proteins involved in cell adhesions and migrations. The cytosolic tails of integrins are essential for transmitting bidirectional signaling and also implicated in maintaining the resting states of the receptors. In addition, cytosolic tails of integrins often undergo post-translation modifications like phosphorylation. However, the consequences of phosphorylation on the structures and interactions are not clear. The leukocyte-specific integrin αMβ2 is essential for myeloid cell adhesion, phagocytosis, and degranulation. In this work, we determined solution structures of the myristoylated cytosolic tail of αM and a Ser phosphorylated variant in dodecylphosphocholine micelles by NMR spectroscopy. Furthermore, the interactions between non-phosphorylated and phosphorylated αM tails with β2 tail were investigated by NMR and fluorescence resonance energy transfer (FRET). The three-dimensional structures of the 24-residue cytosolic tail of αM or phosphorylated αM are characterized by an N-terminal amphipathic helix and a loop at the C terminus. The residues at the loop are involved in packing interactions with the hydrophobic face of the helix. 15N-1H heteronuclear single quantum coherence experiments identified residues of αM and β2 tails that may be involved in the formation of a tail-tail heterocomplex. We further examined interactions between myristoylated β2 tail in dodecylphosphocholine micelles with dansylated αM tail peptides by FRET. These studies revealed enhanced interactions between αM or phosphorylated αM tails with β2 tail with Kd values ∼5.2±0.6 and ∼4.4±0.7 μm, respectively. Docked structures of tail-tail complexes delineated that the αM/β2 interface at the cytosolic region could be sustained by a network of polar interactions, ionic interactions, and/or hydrogen bonds.
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Affiliation(s)
- Geok-Lin Chua
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Xiao-Yan Tang
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Monalisa Amalraj
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Suet-Mien Tan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
| | - Surajit Bhattacharjya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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13
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Naik MU, Nigam A, Manrai P, Millili P, Czymmek K, Sullivan M, Naik UP. CIB1 deficiency results in impaired thrombosis: the potential role of CIB1 in outside-in signaling through integrin alpha IIb beta 3. J Thromb Haemost 2009; 7:1906-14. [PMID: 19691476 PMCID: PMC7034629 DOI: 10.1111/j.1538-7836.2009.03581.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
UNLABELLED Agonist-induced inside-out signaling activates platelet integrin alpha(IIb)beta(3), rendering it to bind plasma fibrinogen (Fg). Fg binding induces outside-in signaling that culminates in platelet aggregation, leading to physiological hemostasis and pathological thrombosis. How outside-in signaling through alpha(IIb)beta(3) regulates hemostasis and thrombosis is not well understood. We have previously shown that CIB1 is involved in regulating alpha(IIb)beta(3) function. OBJECTIVE To determine the in vivo role of CIB1 in the process of hemostasis and thrombosis. METHODS AND RESULTS Genetic ablation of Cib1 significantly increased mouse tail bleeding time. Greater than 50% of the Cib1 null mice showed a rebleeding phenotype. Time taken for complete occlusion of carotid artery upon 10% FeCl(3)-induced injury was significantly delayed in the absence of Cib1. This was also associated with unstable thrombus formation. The inside-out signaling appears normal as ADP-, collagen- and PAR4 peptide-induced aggregation and fibrinogen binding was unaffected. The absence of Cib1 also affected the ability of platelets to spread on immobilized Fg, but not filopodia formation. Spreading could be restored in Cib1 null platelets by the addition of exogenous ADP. Outside-in signaling-dependent tyrosine phosphorylation of the integrin beta(3) subunit was significantly reduced in the absence of Cib1 as determined by Western blot analysis. CONCLUSION Using gene knockout mice, we show for the first time that lack of Cib1 results in impaired thrombosis. CIB1 regulates these processes by affecting platelet spreading, but not platelet filopodia formation. These in vivo and in vitro results clearly show that CIB1 is a key regulator of thrombosis.
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Affiliation(s)
- M U Naik
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA.
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14
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Gene expression microarray analysis encompassing metamorphosis and the onset of calcification in the scleractinian coral Montastraea faveolata. Mar Genomics 2009; 2:149-59. [DOI: 10.1016/j.margen.2009.07.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 07/10/2009] [Accepted: 07/23/2009] [Indexed: 11/18/2022]
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15
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Reilly D, Larkin D, Devocelle M, Fitzgerald DJ, Moran N. Calreticulin-independent regulation of the platelet integrin αIIbβ3by the KVGFFKR αIIb-cytoplasmic motif. Platelets 2009; 15:43-54. [PMID: 14985176 DOI: 10.1080/09537100310001640055] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The platelet integrin alphaIIbbeta3 alters conformation in response to platelet activation and ligand binding, although the molecular mechanisms involved are not known. We previously showed that a lipid modified peptide, corresponding to the membrane proximal 989KVGFFKR995 portion of the alphaIIb cytoplasmic tail, independently activates platelet alphaIIbbeta3. Calreticulin (CRT) is a potential integrin regulatory protein based on its interaction with the highly conserved alpha-integrin sequence KxGFFKR. We therefore examined the possible interaction of calreticulin and alphaIIbbeta3 in human platelets. We demonstrate that calreticulin in platelets is localised to the granulomere. In contrast, the known integrin-binding protein talin accumulates at the periphery of spreading platelets and colocalises with alphaIIbbeta3 during the process of adhesion. An interaction between calreticulin and alphaIIbbeta3 could not be demonstrated using co-immunoprecipitation techniques under various platelet activation states, even in the presence of covalent chemical crosslinkers. Thus, calreticulin does not functionally interact with the major integrin in human platelets. In order to identify proteins that interact with the integrin KVGFFKR motif we then used a peptide 'pull-down' assay from platelet lysates with biotinylated peptides and demonstrate that only the alphaIIb and beta3 subunits selectively and individually interact with this sequence. This interaction is divalent cation-dependent, has high-affinity, and occurs both with purified alphaIIbbeta3 complex and with electroeluted alpha and beta subunits. Thus, our data show that the conserved integrin KVGFFKR domain interacts primarily with the alpha and beta cytoplasmic tails and not with CRT in human platelets.
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Affiliation(s)
- Dermot Reilly
- Centre for Sythesis and Chemical Biology, Department of Chemistry, Royal College of Surgeons in Ireland, Dublin
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16
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Abstract
Integrins are a ubiquitous family of non-covalently associated alpha/beta transmembrane heterodimers linking extracellular ligands to intracellular signaling pathways [1] [Cell, 2002; 110: 673]. Platelets contain five integrins, three beta1 integrins that mediate platelet adhesion to the matrix proteins collagen, fibronectin and laminin, and the beta3 integrins alphavbeta3 and alphaIIbbeta3 [2] [J Clin Invest, 2005; 115: 3363]. While there are only several hundred alphavbeta3 molecules per platelet, alphavbeta3 mediates platelet adhesion to osteopontin and vitronectin in vitro [3] [J Biol Chem, 1997; 272: 8137]; whether this occurs in vivo remains unknown. By contrast, the 80,000 alphaIIbbeta3 molecules on agonist-stimulated platelets bind fibrinogen, von Willebrand factor, and fibronectin, mediating platelet aggregation when the bound proteins crosslink adjacent platelets [2] [J Clin Invest, 2005; 115: 3363]. Although platelet integrins are poised to shift from resting to active conformations, tight regulation of their activity is essential to prevent the formation of intravascular thrombi. This review focuses on the structure and function of the intensively studied beta3 integrins, in particular alphaIIbbeta3, but reference will be made to other integrins where relevant.
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Affiliation(s)
- J S Bennett
- Hematology-Oncology Division, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
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17
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Kato A, Oshimi K. Ancient ubiquitous protein 1 and Syk link cytoplasmic tails of the integrin alpha(IIb)beta(3). Platelets 2009; 20:105-10. [PMID: 19235052 DOI: 10.1080/09537100802641507] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
It is currently accepted that activity of the integrin alpha(IIb)beta(3) is modulated by direct interaction between its cytoplasmic tails (CTs) and association of cytoplasmic proteins with them, and disruption of the close linkage between CTs leads to activation of alpha(IIb)beta(3) (inside-out signaling). We previously reported that ancient ubiquitous protein (Aup1) binds to the membrane-proximal sequence of integrin alphaCTs that plays a pivotal role in the inside-out signaling. To explore biological function of Aup1, we examined in this study interaction of Aup1 with Src and Syk that are quickly activated in platelets before fibrinogen binding following thrombin stimulation. By immunoprecipitation assay with resting platelets, we first found that alpha(IIb)beta(3), Src, Syk, and Aup1 are constitutively complexed. In vitro binding study with recombinant Syk and glutathione (GSH) S-transferase (GST) - Src, -Aup1, and -alpha(IIb) and - beta(3) CTs that are immobilized to GSH- beads revealed direct binding of Syk to Aup1 as well as the beta(3) CT. Dot blot analysis with synthetic peptides for alpha(IIb) and beta(3) CTs, and GST-Aup1 and -Src immobilized to PVDF membrane exhibited concordant result with the GST pull-down assay. Immunoprecipitation of platelet lysates 10 seconds after thrombin stimulation, when activity and tyrosine phosphorylation of Syk are maimum, exhibited that active Syk does not coprecipitate with Aup1. In vitro kinase assay with GST-Syk and -Aup1 proteins at the presence or absence of active Src, a potent activator of Syk, revealed that Aup1 does not directly influence activation of Syk by autophosphorylation or tyrosine phosphorylation by Src. These results indicate that Aup1 is an adaptor recruiting Syk to the alpha(IIb) CT, and suggest that the alpha(IIb) -Aup1- Syk- beta(3) complex formation links alpha(IIb) and beta(3) CTs to sustain alpha(IIb)beta(3) in an inactive state and Syk dissociates from Aup1 after activation.
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Affiliation(s)
- Atsushi Kato
- Division of Hematology, Juntendo University School of Medicine, Bunkyo-ku, Tokyo, Japan.
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18
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Podolnikova NP, O'Toole TE, Haas TA, Lam SCT, Fox JEB, Ugarova TP. Adhesion-induced unclasping of cytoplasmic tails of integrin alpha(IIb)beta3. Biochemistry 2009; 48:617-29. [PMID: 19117493 DOI: 10.1021/bi801751s] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Integrin alpha(IIb)beta(3) plays a pivotal role in hemostasis and thrombosis by mediating adhesive interactions of platelets. Binding of alpha(IIb)beta(3) to its physiological ligands, immobilized fibrinogen and fibrin, induces outside-in signaling in platelets, leading to their adhesion and spreading even without prior stimulation by agonists. Implicit in these phenomena is a requirement for the linkage between integrins' cytoplasmic tails and intracellular proteins. However, the nature of the initiating signal has not been established. In this study, we examined whether binding of alpha(IIb)beta(3) to immobilized fibrin(ogen), per se, triggers interaction of the integrin with cytoplasmic proteins. Using the integrin-binding skelemin fragment as a marker of exposure of residues involved in the clasp between alpha(IIb) and beta(3) cytoplasmic tails, we showed that its binding site in the membrane-proximal beta(3) 715-730 segment is cryptic and becomes exposed as a result of binding of isolated alpha(IIb)beta(3) to immobilized ligands. Furthermore, the skelemin-like protein present in platelets and CHO cells does not associate with alpha(IIb)beta(3) in resting platelets or suspended alpha(IIb)beta(3)-expressing CHO cells but is recruited to integrin during cell adhesion. In addition, not only beta(3) but also the membrane-proximal 989-1000 segment of the alpha(IIb) cytoplasmic tail binds the skelemin fragment. Finally, the same residues, alpha(IIb) Val(990), alpha(IIb) Arg(995), and beta(3) His(722), involved in the formation of the clasp between the tails are also required for skelemin binding. These studies suggest that ligation of alpha(IIb)beta(3) by immobilized ligands during platelet adhesion induces a transmembrane conformation change in the integrin, resulting in unclasping of the complex between the membrane-proximal parts of cytoplasmic tails, thereby unmasking residues involved in binding the skelemin-like protein. Thus, the junction between alpha(IIb) and beta(3) cytoplasmic tails may contain the critical structural information for the initiation of outside-in signaling.
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Affiliation(s)
- Nataly P Podolnikova
- Center for Metabolic Biology, Arizona State University, Tempe, Arizona 85287, USA
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19
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Larkin D, Treumann A, Murphy D, DeChaumont C, Kiernan A, Moran N. Compartmentalization regulates the interaction between the platelet integrin alpha IIb beta 3 and ICln. Br J Haematol 2008; 144:580-90. [PMID: 19055659 DOI: 10.1111/j.1365-2141.2008.07483.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The volume-regulating protein, ICln, interacts with the conserved KxGFFKR alpha-integrin signature motif. ICln is an abundant protein (4455 +/- 650 molecules/platelet) found exclusively in the soluble cytosolic fraction of unactivated platelets. In contrast, its binding partner, the platelet integrin alpha(IIb)beta(3), is present in detergent-insoluble fractions associated with membrane and cytoskeleton subcellular localizations. This study investigated factors that regulate the interaction of ICln with alpha(IIb)beta(3) during platelet activation. His-tagged recombinant ICln bound equally to purified alpha(IIb)beta(3) and to integrin from resting or activated platelets. Binding was not affected by direct integrin activation with Mn(++) or by inhibitors of integrin occupancy (abciximab, RGD). However, the capacity for interaction between integrin and recombinant ICln was slowly downregulated following prolonged platelet activation for >300 s. In parallel, ICln redistributed to membrane and cytoskeletal platelet subcellular fractions. The time-course of this redistribution preceded the downregulation of integrin binding capacity and suggests that only a short window of opportunity exists for ICln interaction with alpha(IIb)beta(3) to occur. Thus, although ICln has the inherent capacity to bind to alpha(IIb)beta(3) regardless of its activation state, it can only do so following platelet activation. Activation-dependent subcellular redistribution of ICln represents a novel, temporally-regulated mechanism for control of integrin function in platelets.
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Affiliation(s)
- Deirdre Larkin
- Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
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20
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WEGENER KATEL, CAMPBELL IAIND. Transmembrane and cytoplasmic domains in integrin activation and protein-protein interactions (review). Mol Membr Biol 2008; 25:376-87. [PMID: 18654929 PMCID: PMC3000922 DOI: 10.1080/09687680802269886] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Integrins are heterodimeric membrane-spanning adhesion receptors that are essential for a wide range of biological functions. Control of integrin conformational states is required for bidirectional signalling across the membrane. Key components of this control mechanism are the transmembrane and cytoplasmic domains of the alpha and beta subunits. These domains are believed to interact, holding the integrin in the inactive state, while inside-out integrin activation is accompanied by domain separation. Although there are strong indications for domain interactions, the majority of evidence is insufficient to precisely define the interaction interface. The current best model of the complex, derived from computational calculations with experimental restraints, suggests that integrin activation by the cytoplasmic protein talin is accomplished by steric disruption of the alpha/beta interface. Better atomic-level resolution structures of the alpha/beta transmembrane/cytoplasmic domain complex are still required for the resting state integrin to corroborate this. Integrin activation is also controlled by competitive interactions involving the cytoplasmic domains, particularly the beta-tails. The concept of the beta integrin tail as a focal adhesion interaction 'hub' for interactions and regulation is discussed. Current efforts to define the structure and affinity of the various complexes formed by integrin tails, and how these interactions are controlled, e.g. by phosphorylation and localization, are described.
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Affiliation(s)
- KATE L. WEGENER
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU. Ph: +44 1865 275346 (IDC) +44 1865 275772 (KLW)
| | - IAIN D. CAMPBELL
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU. Ph: +44 1865 275346 (IDC) +44 1865 275772 (KLW)
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21
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Rodius S, Chaloin O, Moes M, Schaffner-Reckinger E, Landrieu I, Lippens G, Lin M, Zhang J, Kieffer N. The talin rod IBS2 alpha-helix interacts with the beta3 integrin cytoplasmic tail membrane-proximal helix by establishing charge complementary salt bridges. J Biol Chem 2008; 283:24212-23. [PMID: 18577523 DOI: 10.1074/jbc.m709704200] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Talin establishes a major link between integrins and actin filaments and contains two distinct integrin binding sites: one, IBS1, located in the talin head domain and involved in integrin activation and a second, IBS2, that maps to helix 50 of the talin rod domain and is essential for linking integrin beta subunits to the cytoskeleton ( Moes, M., Rodius, S., Coleman, S. J., Monkley, S. J., Goormaghtigh, E., Tremuth, L., Kox, C., van der Holst, P. P., Critchley, D. R., and Kieffer, N. (2007) J. Biol. Chem. 282, 17280-17288 ). Through the combined approach of mutational analysis of the beta3 integrin cytoplasmic tail and the talin rod IBS2 site, SPR binding studies, as well as site-specific antibody inhibition experiments, we provide evidence that the integrin beta3-talin rod interaction relies on a helix-helix association between alpha-helix 50 of the talin rod domain and the membrane-proximal alpha-helix of the beta3 integrin cytoplasmic tail. Moreover, charge complementarity between the highly conserved talin rod IBS2 lysine residues and integrin beta3 glutamic acid residues is necessary for this interaction. Our results support a model in which talin IBS2 binds to the same face of the beta3 subunit cytoplasmic helix as the integrin alphaIIb cytoplasmic tail helix, suggesting that IBS2 can only interact with the beta3 subunit following integrin activation.
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Affiliation(s)
- Sophie Rodius
- Laboratoire de Biologie et Physiologie Intégrée (CNRS/GDRE-ITI), Université du Luxembourg, L-1511 Luxembourg, Grand-Duchy of Luxembourg
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Haas TA, Taherian A, Berry T, Ma X. Identification of residues of functional importance within the central turn motifs present in the cytoplasmic tails of integrin alphaIIb and alphaV subunits. Thromb Res 2008; 122:507-16. [PMID: 18328539 DOI: 10.1016/j.thromres.2008.01.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Revised: 12/17/2007] [Accepted: 01/15/2008] [Indexed: 12/24/2022]
Abstract
INTRODUCTION Previous studies demonstrated that cell-permeable alphaIIb cytoplasmic peptides can modulate the activation of alphaIIbbeta3. An integrin activation motif was mapped to its membrane proximal region and a double proline mutant peptide and receptor indicated that its central turn motif had inhibitory capacity. However, the residues critical for inhibition of alphaIIbbeta3 activation were not identified. Using central turn peptides derived from alphaIIb and alphaV, residues critical for suppression of integrin activation were identified and the importance of these residues in protein-protein interactions was assessed. MATERIALS AND METHODS Cell-permeable peptides were used to determine the capacity of the central turn peptides to suppress alphaIIbbeta3 and alphaVbeta3 activation. Far Western analysis was used to characterize the capacity of the peptides to interact with CIB1 and surface plasmon resonance was used to characterize the binding of an antibody to the cytoplasmic tails of alphaIIb and alphaV. RESULTS AND CONCLUSIONS The central turn peptide from alphaV, alphaV(993-1001), has full inhibitory capacity while that derived from alphaIIb requires additional residues located adjacent to alphaIIb(995-1003). Within these two sequences there is a switch in the position of an asparaginine and leucine residue for a valine and glutamine (alphaIIb, RNRPPLEED; alphaV, RVRPPQEEQ). This switch had a dramatic effect on their inhibitory capacity and on protein-protein interactions. The two arginine and glutamic residues, juxtapositioned at identical locations in both subunits, appeared to be important in specifying the orientation by which proteins can dock to this region in alphaIIb and alphaV.
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Affiliation(s)
- Thomas A Haas
- Department of Anatomy and Cell Biology, College of Medicine, University of Saskatchewan, Saskatoon, SK, Canada S7N 5E5.
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Shi X, Ma YQ, Tu Y, Chen K, Wu S, Fukuda K, Qin J, Plow EF, Wu C. The MIG-2/integrin interaction strengthens cell-matrix adhesion and modulates cell motility. J Biol Chem 2007; 282:20455-66. [PMID: 17513299 DOI: 10.1074/jbc.m611680200] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Integrin-mediated cell-matrix adhesion plays an important role in control of cell behavior. We report here that MIG-2, a widely expressed focal adhesion protein, interacts with beta1 and beta3 integrin cytoplasmic domains. Integrin binding is mediated by a single site within the MIG-2 FERM domain. Functionally, the MIG-2/integrin interaction recruits MIG-2 to focal adhesions. Furthermore, using alphaIIbbeta3 integrin-expressing Chinese hamster ovary cells, a well described model system for integrin activation, we show that MIG-2 promotes integrin activation and enhances cell-extracellular matrix adhesion. Although MIG-2 is expressed in many cell types, it is deficient in certain colon cancer cells. Expression of MIG-2, but not of an integrin binding-defective MIG-2 mutant, in MIG-2-null colon cancer cells strengthened cell-matrix adhesion, promoted focal adhesion formation, and reduced cell motility. These results suggest that the MIG-2/integrin interaction is an important element in the cellular control of integrin-mediated cell-matrix adhesion and that loss of this interaction likely contributes to high motility of colon cancer cells.
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Affiliation(s)
- Xiaohua Shi
- Department of Pathology, University of Pittsburgh School of Medicine, 3550 Terrace Street, Pittsburgh, PA 15261, USA
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24
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Moes M, Rodius S, Coleman SJ, Monkley SJ, Goormaghtigh E, Tremuth L, Kox C, van der Holst PPG, Critchley DR, Kieffer N. The integrin binding site 2 (IBS2) in the talin rod domain is essential for linking integrin beta subunits to the cytoskeleton. J Biol Chem 2007; 282:17280-8. [PMID: 17430904 DOI: 10.1074/jbc.m611846200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Talin1 is a large cytoskeletal protein that links integrins to actin filaments through two distinct integrin binding sites, one present in the talin head domain (IBS1) necessary for integrin activation and a second (IBS2) that we have previously mapped to talin residues 1984-2113 (fragment J) of the talin rod domain (1 Tremuth, L., Kreis, S., Melchior, C., Hoebeke, J., Ronde, P., Plancon, S., Takeda, K., and Kieffer, N. (2004) J. Biol. Chem. 279, 22258-22266), but whose functional role is still elusive. Using a bioinformatics and cell biology approach, we have determined the minimal structure of IBS2 and show that this integrin binding site corresponds to 23 residues located in alpha helix 50 of the talin rod domain (residues 2077-2099). Alanine mutation of 2 highly conserved residues (L2094A/I2095A) within this alpha helix, which disrupted the alpha-helical structure of IBS2 as demonstrated by infrared spectroscopy and limited trypsin proteolysis, was sufficient to prevent in vivo talin fragment J targeting to alphaIIbbeta3 integrin in focal adhesions and to inhibit in vitro this association as shown by an alphaIIbbeta3 pulldown assay. Moreover, expression of a full-length mouse green fluorescent protein-talin LI/AA mutant in mouse talin1(-/-) cells was unable to rescue the inability of these cells to assemble focal adhesions (in contrast to green fluorescent protein-talin wild type) despite the presence of IBS1. Our data provide the first direct evidence that IBS2 in the talin rod is essential to link integrins to the cytoskeleton.
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Affiliation(s)
- Michèle Moes
- Laboratoire de Biologie et Physiologie Intégrée (CNRS/GDRE-ITI), University of Luxembourg, L-1511 Luxembourg, Grand Duchy of Luxembourg, Luxembourg
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Ma YQ, Yang J, Pesho MM, Vinogradova O, Qin J, Plow EF. Regulation of integrin alphaIIbbeta3 activation by distinct regions of its cytoplasmic tails. Biochemistry 2006; 45:6656-62. [PMID: 16716076 DOI: 10.1021/bi060279h] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The short cytoplasmic tails regulate activation of integrin adhesion receptors via clasping/unclasping of their membrane-proximal helices. Using integrin alpha(IIb)beta(3) as a model, we show that a previously reported activating mutation alpha(IIb)(R(995)D) that perturbs the electrostatic interface in the clasp only partially activates alpha(IIb)beta(3) and that extensive activation of the receptor is achieved by complete deletion of alpha(IIb) CT or triple mutations in alpha(IIb)(V(990)A/F(992)A/R(995)D) that disrupt both electrostatic and hydrophobic interfaces in the clasp. The results provide quantitative evidence for an equilibrium-based integrin activation process where shifting the equilibrium to the fully activated state requires total unclasping of the cytoplasmic tails. We further demonstrate that while the C-terminal region of the alpha(IIb) tail minimally influences alpha(IIb)beta(3) activation, the C-terminal region of the beta(3) tail is critically involved. A disease-causing mutation of S(752)P in this region, but not S(752)A, suppressed partial activation induced by R(995)D or the talin head domain but did not affect activation induced by alpha(IIb) truncation. NMR spectroscopy revealed that S(752)P but not the S(752)A mutation disrupted a C-terminal helix within the beta(3) tail, suggesting that the C-terminal helix may regulate the equilibrium-based clasping/unclasping process. Together, these data provide molecular insights into how distinct regions of the cytoplasmic tails differentially and cooperatively regulate integrin activation.
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Affiliation(s)
- Yan-Qing Ma
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA
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Liu QY, Corjay M, Feuerstein GZ, Nambi P. Identification and characterization of triosephosphate isomerase that specifically interacts with the integrin alphaIIb cytoplasmic domain. Biochem Pharmacol 2006; 72:551-7. [PMID: 16859644 DOI: 10.1016/j.bcp.2006.05.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 05/23/2006] [Accepted: 05/24/2006] [Indexed: 11/17/2022]
Abstract
Integrin alphaIIb/beta3 (IIb/IIIa), a platelet fibrinogen receptor, has been shown to play a critical role in thrombosis and hemostasis. However, the mechanisms by which ligands interact with the alphaIIb/beta3 receptor is not very clear at this time. The interaction between the ligand, the receptor and the transmission of extracellular signals may involve the cytoplasmic domains of these integrins. The objective of this investigation was to identify novel proteins that interact with the cytoplasmic tail of alphaIIb. Using alphaIIb cytoplasmic tail as the bait and a yeast two-hybrid system, we have identified three separate clones containing inserts that encoded the same protein with different truncated N-terminals. Sequence analysis showed that the inserts of the three clones encoded a previously identified enzyme: triose phosphate isomerase (TPI). In addition, we demonstrated that TPI failed to interact with the integrin alpha2 tail, beta3 tail and lamin, but showed a weak binding to the alphaV tail which shares the highest homology with alphaIIb tail among the integrin alpha family. Site-directed mutagenesis studies around the homology region indicated that the critical peptide sequence necessary for the interaction between TPI and alphaIIb tail is GFFKRNRPPLEE. Using RT-PCR, we have demonstrated the presence of TPI mRNA in platelets. In addition, experiments were also performed to demonstrate specific binding of TPI to alphaIIb using an ELISA and fusion protein. Taken together, these data suggest that TPI specifically interacts with alphaIIb and may play a critical role in alphaIIb/beta3-mediated platelet function.
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Affiliation(s)
- Qiang-Yuan Liu
- Du Pont Pharmaceuticals, Route 141 & Henry Road, Wilmington, DE 19880, USA
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29
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Abstract
The platelet integrin alpha(IIb)beta(3) is required for platelet aggregation. Like other integrins, alpha(IIb)beta(3) resides on cell surfaces in an equilibrium between inactive and active conformations. Recent experiments suggest that the shift between these conformations involves a global reorganization of the alpha(IIb)beta(3) molecule and disruption of constraints imposed by the heteromeric association of the alpha(IIb) and beta(3) transmembrane and cytoplasmic domains. The biochemical, biophysical, and ultrastructural results that support this conclusion are discussed in this Review.
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Affiliation(s)
- Joel S Bennett
- Hematology-Oncology Division, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6058, USA.
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30
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Yuan W, Leisner TM, McFadden AW, Wang Z, Larson MK, Clark S, Boudignon-Proudhon C, Lam SCT, Parise LV. CIB1 is an endogenous inhibitor of agonist-induced integrin alphaIIbbeta3 activation. J Cell Biol 2006; 172:169-75. [PMID: 16418530 PMCID: PMC2063547 DOI: 10.1083/jcb.200505131] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2005] [Accepted: 12/09/2005] [Indexed: 01/15/2023] Open
Abstract
In response to agonist stimulation, the alphaIIbbeta3 integrin on platelets is converted to an active conformation that binds fibrinogen and mediates platelet aggregation. This process contributes to both normal hemostasis and thrombosis. Activation of alphaIIbbeta3 is believed to occur in part via engagement of the beta3 cytoplasmic tail with talin; however, the role of the alphaIIb tail and its potential binding partners in regulating alphaIIbbeta3 activation is less clear. We report that calcium and integrin binding protein 1 (CIB1), which interacts directly with the alphaIIb tail, is an endogenous inhibitor of alphaIIbbeta3 activation; overexpression of CIB1 in megakaryocytes blocks agonist-induced alphaIIbbeta3 activation, whereas reduction of endogenous CIB1 via RNA interference enhances activation. CIB1 appears to inhibit integrin activation by competing with talin for binding to alphaIIbbeta3, thus providing a model for tightly controlled regulation of alphaIIbbeta3 activation.
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Affiliation(s)
- Weiping Yuan
- Department of Pharmacology, Dental Research Center, Carolina Cardiovascular Biology Center, and Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC 27599
| | - Tina M. Leisner
- Department of Pharmacology, Dental Research Center, Carolina Cardiovascular Biology Center, and Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC 27599
| | - Andrew W. McFadden
- Department of Pharmacology, Dental Research Center, Carolina Cardiovascular Biology Center, and Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC 27599
| | - Zhengyan Wang
- Department of Pharmacology, Dental Research Center, Carolina Cardiovascular Biology Center, and Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC 27599
| | - Mark K. Larson
- Department of Pharmacology, Dental Research Center, Carolina Cardiovascular Biology Center, and Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC 27599
| | - Shantres Clark
- Department of Pharmacology, Dental Research Center, Carolina Cardiovascular Biology Center, and Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC 27599
| | - Christel Boudignon-Proudhon
- Department of Pharmacology, Dental Research Center, Carolina Cardiovascular Biology Center, and Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC 27599
| | - Stephen C.-T. Lam
- Department of Pharmacology, University of Illinois, Chicago, IL 60680
| | - Leslie V. Parise
- Department of Pharmacology, Dental Research Center, Carolina Cardiovascular Biology Center, and Lineberger Cancer Center, University of North Carolina, Chapel Hill, NC 27599
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31
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Wu PL, Lee SC, Chuang CC, Mori S, Akakura N, Wu WG, Takada Y. Non-cytotoxic cobra cardiotoxin A5 binds to alpha(v)beta3 integrin and inhibits bone resorption. Identification of cardiotoxins as non-RGD integrin-binding proteins of the Ly-6 family. J Biol Chem 2006; 281:7937-45. [PMID: 16407244 DOI: 10.1074/jbc.m513035200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Severe tissue necrosis with a retarded wound healing process is a major symptom of a cobra snakebite. Cardiotoxins (CTXs) are major components of cobra venoms that belong to the Ly-6 protein family and are implicated in tissue damage. The interaction of the major CTX from Taiwan cobra, i.e. CTX A3, with sulfatides in the cell membrane has recently been shown to induce pore formation and cell internalization and to be responsible for cytotoxicity in cardiomyocytes (Wang, C.-H., Liu, J.-H., Lee, S.-C., Hsiao, C.-D., and Wu, W.-g. (2006) J. Biol. Chem. 281, 656-667). We show here that one of the non-cytotoxic CTXs, i.e. CTX A5 or cardiotoxin-like basic polypeptide, from Taiwan cobra specifically bound to alpha(v)beta3 integrin and inhibited bone resorption activity. We found that both membrane-bound and recombinant soluble alpha(v)beta3 integrins bound specifically to CTX A5 in a dose-dependent manner. Surface plasmon resonance analysis showed that human soluble alpha(v)beta3 bound to CTX A5 with an apparent affinity of approximately 0.3 microM. Calf pulmonary artery endothelial cells, which constitutively express alpha(v)beta3, showed a CTX A5 binding profile similar to that of membrane-bound and soluble alpha(v)beta3 integrins, suggesting that endothelial cells are a potential target for CTX action. We tested whether CTX A5 inhibits osteoclast differentiation and bone resorption, a process known to be involved in alpha(v)beta3 binding and inhibited by RGD-containing peptides. We demonstrate that CTX A5 inhibited both activities at a micromolar range by binding to murine alpha(v)beta3 integrin in osteoclasts and that CTX A5 co-localized with beta3 integrin. Finally, after comparing the integrin binding affinity among CTX homologs, we propose that the amino acid residues near the two loops of CTX A5 are involved in integrin binding. These results identify CTX A5 as a non-RGD integrin-binding protein with therapeutic potential as an integrin antagonist.
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Affiliation(s)
- Po-Long Wu
- Institute of Bioinformatics and Structural Biology, National Tsing Hua University, Hsinchu 30043, Taiwan
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32
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Abstract
The development and integrity of the cardiovascular system depends on integrins, a family of adhesion receptors, vitally important for homeostasis of animal species from fruit fly to man. Integrins are critical players in cell migration, cell adhesion, cell cycle progression, differentiation, and apoptosis. Consequently, integrins have a major impact on the patterning and functions of the blood and cardiovascular system. Integrins undergo conformational changes, which alter their affinity for ligands through a process operationally defined as integrin activation. Integrin activation is important for platelet aggregation, leukocyte extravasation, and cell adhesion and migration, thus influencing such processes as hemostasis, inflammation and angiogenesis. Recently, a series of studies have begun to define the mechanism of integrin activation by demonstrating that binding of a cytoskeletal protein, talin, to integrin beta subunit cytoplasmic tail is a last common step in integrin activation. These findings indicate that talin is likely to be at the center of converging signaling pathways regulating integrin activation.
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Affiliation(s)
- B I Ratnikov
- Department of Medicine, University of California San Diego, La Jolla, CA 92093-0726, USA
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33
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Blamey CJ, Ceccarelli C, Naik UP, Bahnson BJ. The crystal structure of calcium- and integrin-binding protein 1: insights into redox regulated functions. Protein Sci 2005; 14:1214-21. [PMID: 15840829 PMCID: PMC2253279 DOI: 10.1110/ps.041270805] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Calcium- and integrin-binding protein 1 (CIB1) is involved in the process of platelet aggregation by binding the cytoplasmic tail of the alpha(IIb) subunit of the platelet-specific integrin alpha(Iib)beta(3). Although poorly understood, it is widely believed that CIB1 acts as a global signaling regulator because it is expressed in many tissues that do not express integrin alpha(Iib)beta(3). We report the structure of human CIB1 to a resolution of 2.3 A, crystallized as a dimer. The dimer interface includes an extensive hydrophobic patch in a crystal form with 80% solvent content. Although the dimer form of CIB1 may not be physiologically relevant, this intersub-unit surface is likely to be linked to alpha(IIb) binding and to the binding of other signaling partner proteins. The C-terminal domain of CIB1 is structurally similar to other EF-hand proteins such as calmodulin and calcineurin B. Despite structural homology to the C-terminal domain, the N-terminal domain of CIB1 lacks calcium-binding sites. The structure of CIB1 revealed a complex with a molecule of glutathione in the reduced state bond to the N-terminal domain of one of the two subunits poised to interact with the free thiol of C35. Glutathione bound in this fashion suggests CIB1 may be redox regulated. Next to the bound GSH, the orientation of residues C35, H31, and S48 is suggestive of a cysteine-type protein phosphatase active site. The potential enzymatic activity of CIB1 is discussed and suggests a mechanism by which it regulates a wide variety of proteins in cells in addition to platelets.
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Affiliation(s)
- Chad J Blamey
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
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34
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Yamniuk AP, Vogel HJ. Calcium- and magnesium-dependent interactions between calcium- and integrin-binding protein and the integrin alphaIIb cytoplasmic domain. Protein Sci 2005; 14:1429-37. [PMID: 15883187 PMCID: PMC2253396 DOI: 10.1110/ps.041312805] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Calcium- and integrin-binding protein (CIB) is a small EF-hand calcium-binding protein that is involved in hemostasis through its interaction with the alphaIIb cytoplasmic domain of integrinalphaIIbbeta(3). We have previously demonstrated that CIB lacks structural stability in the absence of divalent metal ions but that it acquires a well-folded conformation upon addition of Ca(2+) or Mg(2+). Here, we have used fluorescence spectroscopy, NMR spectroscopy, and isothermal titration calorimetry to demonstrate that both Ca(2+)-bound CIB (Ca(2+)-CIB) and the Mg(2+)-bound protein (Mg(2+)-CIB) bind with high affinity and through a similar mechanism to alphaIIb cytoplasmic domain peptides, but that metal-free CIB (apo-CIB) binds in a different manner. The interactions are thermodynamically distinct for Ca(2+)-CIB and Mg(2+)-CIB, but involve hydrophobic interactions in each case. Since the Mg(2+) concentration inside the cell is sufficient to saturate CIB at all times, our results imply that CIB would be capable of binding to the alphaIIb cytoplasmic domain independent of an intracellular Ca(2+) stimulus in vivo. This raises the question of whether CIB can act as a Ca(2+) sensor in alphaIIbbeta(3) signaling or if other regulatory mechanisms such as fibrinogen-induced conformational changes in alphaIIbbeta(3), post-translational modifications, or the binding of other accessory proteins mediate the interactions between CIB and alphaIIbbeta(3). Differences in NMR spectra do suggest, however, that Ca(2+)-binding to the Mg(2+)- CIB-alphaIIb complex induces subtle structural changes that could further modulate the activity of alphaIIbbeta(3).
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Affiliation(s)
- Aaron P Yamniuk
- Structural Biology Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4
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35
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Litvinov RI, Nagaswami C, Vilaire G, Shuman H, Bennett JS, Weisel JW. Functional and structural correlations of individual αIIbβ3 molecules. Blood 2004; 104:3979-85. [PMID: 15319287 DOI: 10.1182/blood-2004-04-1411] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe divalent cation Mn2+ and the reducing agent dithiothreitol directly shift integrins from their inactive to their active states. We used transmission electron microscopy and laser tweezers-based force spectroscopy to determine whether structural rearrangements induced by these agents in the integrin αIIbβ3 correlate with its ability to bind fibrinogen. Mn2+ increased the probability of specific fibrinogen-αIIbβ3 interactions nearly 20-fold in platelets, and both Mn2+ and dithiothreitol increased the probability more than 2-fold using purified proteins. Of 3 αIIbβ3 conformations, closed with stalks touching, open with stalks separated, and globular without visible stalks, Mn2+ and dithiothreitol induced a significant increase in the proportion of open structures, as well as structural changes in the αIIbβ3 headpiece. Mn2+ also increased the number of complexes between fibrinogen and purified αIIbβ3 molecules, all of which were in the open conformation. Finally, Mn2+ induced the formation of αIIbβ3 clusters that resulted from interactions exclusively involving the distal ends of the stalks. These results indicate that there is a direct correlation between αIIbβ3 activation and the overall conformation of the molecule. Further, they are consistent with the presence of a linked equilibrium between single inactive and single active αIIbβ3 molecules and active αIIbβ3 clusters. (Blood. 2004;104:3979-3985)
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Affiliation(s)
- Rustem I Litvinov
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, 421 Curie Blvd, 1054 BRB II/III, Philadelphia, PA 19104-6058, USA
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36
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Abstract
The ability of cells to regulate dynamically their adhesion to one another and to the extracellular matrix (ECM) that surrounds them is essential in multicellular organisms. The integrin family of transmembrane adhesion receptors mediates both cell-cell and cell-ECM adhesion. One important, rapid and reversible mechanism for regulating adhesion is by increasing the affinity of integrin receptors for their extracellular ligands (integrin activation). This is controlled by intracellular signals that, through their action on integrin cytoplasmic domains, induce conformational changes in integrin extracellular domains that result in increased affinity for ligand. Recent studies have shed light on the final intracellular steps in this process and have revealed a vital role for the cytoskeletal protein talin.
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Affiliation(s)
- David A Calderwood
- Department of Pharmacology, Yale University School of Medicine, Sterling Hall of Medicine, New Haven, CT 06520, USA.
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37
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Zhu J, Stabler SM, Ames JB, Baskakov I, Monteiro MJ. Calcium binding sequences in calmyrin regulates interaction with presenilin-2. Exp Cell Res 2004; 300:440-54. [PMID: 15475008 DOI: 10.1016/j.yexcr.2004.07.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2004] [Revised: 07/13/2004] [Indexed: 11/21/2022]
Abstract
Calmyrin is a myristoylated calcium binding protein that contains four putative EF-hands. Calmyrin interacts with a number of proteins, including presenilin-2 (PS2). However, the biophysical properties of calmyrin, and the molecular mechanisms that regulate its binding to different partners, are not well understood. By site-directed mutagenesis and Ca2+ binding studies, we found that calmyrin binds two Ca2+ ions with a dissociation constant of approximately 53 microM, and that the two C-terminal EF-hands 3 and 4 bind calcium. Using ultraviolet spectroscopy, circular dichroism (CD), and NMR, we found that Ca(2+)-free and -bound calmyrin have substantially different protein conformations. By yeast two-hybrid assays, we found that both EF-hands 3 and 4 of calmyrin must be intact for calmyrin to interact with PS2-loop sequences. Pulse-chase studies of HeLa cells transfected with calmyrin expression constructs indicated that wild-type (Wt) calmyrin has a half-life of approximately 75 min, whereas a mutant defective in myristoylation turns over more rapidly (half-life of 35 min). By contrast, the half-lives of calmyrin mutants with a disrupted EF-hand 3 or EF-hand 4 were 52 and 170 min, respectively. Using immunofluorescence staining of HeLa cells transfected with Wt and mutant calmyrin cDNAs, we found that both calcium binding and myristoylation are important for dynamic intracellular targeting of calmyrin. Double immunofluorescence microscopy indicated that Wt and myristoylation-defective calmyrin proteins colocalize efficiently and to the same extent with PS2, whereas calmyrin mutants defective in calcium binding display less colocalization with PS2. Our results suggest that calmyrin functions as a calcium sensor and that calcium binding sequences in calmyrin are important for interaction with the PS2 loop.
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Affiliation(s)
- Jingsong Zhu
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD 21201, USA
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38
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Campbell ID, Ginsberg MH. The talin-tail interaction places integrin activation on FERM ground. Trends Biochem Sci 2004; 29:429-35. [PMID: 15362227 DOI: 10.1016/j.tibs.2004.06.005] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Integrins are essential receptors for the development and functioning of multicellular animals because they mediate cell migration and cell adhesion, and regulate cell proliferation and apoptosis. Cellular regulation of the affinity of integrins for ligands - so-called 'integrin activation' - is a central property of these receptors. Integrin activation controls cell adhesion, migration and extracellular matrix assembly, thereby contributing to processes such as angiogenesis, tumor cell metastasis, inflammation, the immune response and hemostasis. Recent studies indicate that a crucial, final step in integrin activation is the binding of talin, a cytoskeletal protein, to the cytoplasmic domain of the integrin beta subunit. These results provide a focus for unraveling the many biochemical pathways implicated in integrin activation and suggest a general structural model for the connections between integrins and diverse cellular signal transduction pathways.
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Affiliation(s)
- Iain D Campbell
- Department of Biochemistry, University of Oxford, Oxford, UK OX1 3QU.
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39
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Calvete JJ. Structures of integrin domains and concerted conformational changes in the bidirectional signaling mechanism of alphaIIbbeta3. Exp Biol Med (Maywood) 2004; 229:732-44. [PMID: 15337827 DOI: 10.1177/153537020422900805] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Integrins are heterodimeric type I transmembrane cell-adhesive receptors whose affinity for ligands is regulated by tertiary and quaternary conformational changes that are transmitted from the cytoplasmic tails to the extracellular ectodomains during the transition from the inactive to the active state. Receptor occupancy initiates further structural alterations that transduce signals across the plasma membrane and result in receptor clustering and recruitment of signaling molecules and cytoskeletal rearrangements at the integrin's cytoplasmic domains. The large distance between the intracellular cytoplasmic domains and the ligand-binding site, which in an extended conformation spans more that 200 A, imposes a complex mechanism of interdomain communication for the bidirectional information flow across the plasma membrane. Significant progress has recently been made in elucidating the crystal and electron microscopy structures of integrin ectodomains in its unliganded and liganded states, and the nuclear magnetic resonance solution structures of stalk domains and the cytoplasmic tails. These structures revealed the location of sites that are functionally important and provided the basis for defining new models of integrin activation and signaling through bidirectional conformational changes, and for understanding the structural basis of the cation-dependent ligand-binding specificity of integrins. Platelet integrin alphaIIbbeta3 has served as a paradigm for many aspects of the structure and function of integrins The aim of this minireview is to combine recent structural and biochemical studies on integrin receptors that converge into a model of the tertiary and quaternary conformational changes in alphaIIbbeta3 and other homologous integrins that propagate inside-out and outside-in signals.
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Affiliation(s)
- Juan J Calvete
- Instituto de Biomedicina de Valencia, C.S.I.C., 46010, Valencia, Spain.
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40
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Yamniuk AP, Nguyen LT, Hoang TT, Vogel HJ. Metal Ion Binding Properties and Conformational States of Calcium- and Integrin-Binding Protein. Biochemistry 2004; 43:2558-68. [PMID: 14992593 DOI: 10.1021/bi035432b] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Calcium- and integrin-binding protein (CIB) is a novel member of the helix-loop-helix family of regulatory calcium-binding proteins which likely has a specific function in hemostasis through its interaction with platelet integrin alphaIIbbeta(3). The significant amino acid sequence homology between CIB and other regulatory calcium-binding proteins such as calmodulin, calcineurin B, and recoverin suggests that CIB may undergo a calcium-induced conformational change; however, the mechanism of calcium binding and the details of a structural change have not yet been investigated. Consequently, we have performed a variety of spectroscopic and microcalorimetric studies of CIB to determine its calcium binding characteristics, and the subsequent conformational changes that occur. Furthermore, we provide the first evidence for magnesium binding to CIB and determine the structural consequences of this interaction. Our results indicate that in the absence of any bound metal ions, apo-CIB adopts a folded yet highly flexible molten globule-like structure. Both calcium and magnesium binding induce conformational changes which stabilize both the secondary and tertiary structure of CIB, resulting in considerable increases in the thermal stability of the proteins. CIB was found to bind two Ca(2+) ions in a sequential manner with dissociation constants (K(d)) near 0.54 and 1.9 microM for sites EF-4 and EF-3, respectively. In contrast, CIB bound only one Mg(2+) ion to EF-3 with a K(d) near 120 microM. Together, our results suggest that CIB may exist in multiple structural and metal ion-bound states in vivo which may play a role in its regulation of target proteins such as platelet integrin.
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Affiliation(s)
- Aaron P Yamniuk
- Structural Biology Research Group, Department of Biological Sciences, University of Calgary, 2500 University Drive Northwest, Calgary, Alberta, Canada T2N 1N4
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41
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Alahari SK, Nasrallah H. A membrane proximal region of the integrin alpha5 subunit is important for its interaction with nischarin. Biochem J 2004; 377:449-57. [PMID: 14535848 PMCID: PMC1223876 DOI: 10.1042/bj20030411] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2003] [Revised: 09/17/2003] [Accepted: 10/09/2003] [Indexed: 11/17/2022]
Abstract
In a previous study [Alahari, Lee and Juliano (2000) J. Cell Biol. 151, 1141-1154], we have identified a novel protein, nischarin, that specifically interacts with the cytoplasmic tail of the alpha5 integrin subunit. Overexpression of this protein profoundly affects cell migration. To examine the nischarin-alpha5 interaction in detail, and to find the minimal region required for the interaction, several mutants of nischarin and alpha5 were created. The results obtained for the yeast two-hybrid system indicate that a 99-aminoacid region of nischarin (from residues 464 to 562) is indispensable for the interaction. Also, we demonstrate that the membrane proximal region (from residues 1017 to 1030) of the alpha5 cytoplasmic tail is essential for the interaction. To characterize more directly the properties of the interaction between nischarin and alpha5, we performed surface-plasmon resonance studies in which peptides were immobilized on the surface of a sensor chip, and the recombinant nischarin protein fragments were injected. Consistent with the two-hybrid results, recombinant nischarin binds well to immobilized alpha5 peptides. In addition, mutational analysis revealed that residues Tyr(1018) and Lys(1022) are crucial for alpha5-nischarin interactions. These results provide evidence that nischarin is capable of directly and selectively binding to a portion of the alpha5 cytoplasmic domain. Further studies demonstrated that the minimal alpha5 binding region of nischarin does not affect cell migration.
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Affiliation(s)
- Suresh K Alahari
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7365, USA.
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42
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Schneider D, Engelman DM. Involvement of transmembrane domain interactions in signal transduction by alpha/beta integrins. J Biol Chem 2003; 279:9840-6. [PMID: 14681217 DOI: 10.1074/jbc.m312749200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The alpha and beta subunits of alpha/beta heterodimeric integrins function together to bind ligands in the extracellular region and transduce signals across cellular membranes. A possible function for the transmembrane regions in integrin signaling has been proposed from structural and computational data. We have analyzed the capacity of the integrin alpha(2), alpha(IIb), alpha(4), beta(1), beta(3), and beta(7) transmembrane domains to form homodimers and/or heterodimers. Our data suggest that the integrin transmembrane helices can help to stabilize heterodimeric integrins but that the interactions do not specifically associate particular pairs of alpha and beta subunits; rather, the alpha/beta subunit interaction constrains the extramembranous domains, facilitating signal transduction by a promiscuous transmembrane helix-helix association.
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Affiliation(s)
- Dirk Schneider
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8114, USA
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43
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Naik UP, Naik MU. Association of CIB with GPIIb/IIIa during outside-in signaling is required for platelet spreading on fibrinogen. Blood 2003; 102:1355-62. [PMID: 12714504 DOI: 10.1182/blood-2003-02-0591] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Platelet spreading on immobilized fibrinogen (Fg) involves progression through a number of morphologic stages that, although distinctive, are not well understood mechanistically. Here we demonstrate that an association between GPIIb/IIIa and calcium- and integrin-binding protein (CIB) is required for the process of platelet spreading. Upon platelet adhesion to immobilized Fg, CIB localizes to the transiently formed filopodia and then redistributes diffusely along the membrane periphery of spread platelets. Immunoprecipitation analyses indicate that CIB and glycoprotein IIb/IIIa (GPIIb/IIIa) interact with each other as platelets adhere to immobilized Fg, and together they associate with the platelet cytoskeleton. Introduction of anti-CIB antibody or GPIIb cytoplasmic peptide into platelets blocks lamellipodia but not filopodia formation. GPIIb peptide-induced inhibition of platelet spreading is recovered by the incorporation of recombinant CIB protein, suggesting that interaction between CIB and GPIIb/IIIa is required for progression from filopodial to spread morphologies. Further, anti-CIB- or GPIIb peptide-induced inhibition of platelet spreading can be overcome by the addition of exogenous adenosine diphosphate (ADP). These data suggest that formation of the CIB-GPIIb/IIIa complex may be necessary for initiation of downstream signaling events, such as ADP secretion, that lead to platelet spreading.
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Affiliation(s)
- Ulhas P Naik
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA.
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44
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Abstract
Integrins are cell adhesion receptors that couple extracellular divalent cation-dependent recognition events with intracellular mechanical and biochemical responses and vice versa, thus affecting every function of nucleated cells. The structural basis of this bidirectional signaling and its dependency on cations has been the focus of intensive study over the past three decades. Significant progress made recently in elucidating the three-dimensional structure of the extracellular and cytoplasmic segments of integrins is giving valuable new insights into the tertiary and quaternary changes that underlie activation, ligand recognition and signaling by these receptors.
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Affiliation(s)
- J-P Xiong
- Renal Unit, Leukocyte Biology & Inflammation Program, Structural Biology Program, Massachusetts General Hospital, Charlestown, MA 02129, USA
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45
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Abstract
AlphaIIbbeta3, the major membrane protein on the surface of platelets, is a member of the integrin family of heterodimeric adhesion receptors. The alphaIIb and beta3 subunits are each composed of a short cytoplasmic tail, a single transmembrane domain, and a large, extracellular region that consists of a series of linked domains. Recent structural analyses have provided insights into the organization of this and other integrins and how a signal is initiated at its cytoplasmic tail to transform the extracellular domain of alphaIIbbeta3 into a functional receptor for fibrinogen or von Willebrand factor to support platelet aggregation and thrombus formation. These functions of alphaIIbbeta3 have been targeted for antithrombotic therapy, and intravenous alphaIIbbeta3 antagonists have been remarkably effective in the setting of percutaneous coronary interventions, showing both short-term and long-term mortality benefits. However, the development of oral antagonists has been abandoned on the basis of excess of mortality in clinical trials, and the extension of therapy with existing alphaIIbbeta3 antagonists to broadly treat acute coronary syndromes has not fully met expectations. An in-depth understanding of how antagonists engage and influence the function of alphaIIbbeta3 and platelets in the context of the new structural insights may explain its salutary and potential deleterious effects.
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Affiliation(s)
- Martin J Quinn
- Joseph J. Jacobs Center for Thrombosis and Vascular Biology, Department of Molecular Cardiology/NB50, Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, Ohio 44195, USA
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46
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Travis MA, Humphries JD, Humphries MJ. An unraveling tale of how integrins are activated from within. Trends Pharmacol Sci 2003; 24:192-7. [PMID: 12707006 DOI: 10.1016/s0165-6147(03)00069-5] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Integrin cytoplasmic tail domains are short, but are essential for normal receptor function because of their key role in relaying bidirectional signals across the plasma membrane. Although it is well established that the cytoplasmic tails both initiate signalling pathways inside the cell and control the transition of integrins from a resting to a ligand-binding competent state, until recently the structural basis of these changes has been unclear. In the past year, however, a series of structural studies has revealed certain features of cytoplasmic domain function, and in this review we focus on how these advances have enlightened our understanding of integrin tail structure and function.
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Affiliation(s)
- Mark A Travis
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, University of Manchester, 2.205 Stopford Building, Oxford Road, Manchester M13 9PT, UK
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47
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Moses JP, Inayathullah NM, Murugesan M, Andrews ME, Balasubramanian MP, Jayakumar R. Effect of Ca2+ on the self assembly of a nonionic peptide aggregate. Int J Pept Res Ther 2003. [DOI: 10.1007/bf02443639] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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48
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Abstract
In their roles as major adhesion receptors, integrins signal across the plasma membrane in both directions. Recent structural and cell biological data suggest models for how integrins transmit signals between their extracellular ligand binding adhesion sites and their cytoplasmic domains, which link to the cytoskeleton and to signal transduction pathways. Long-range conformational changes couple these functions via allosteric equilibria.
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Affiliation(s)
- Richard O Hynes
- Howard Hughes Medical Institute, Center for Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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49
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Vinogradova O, Velyvis A, Velyviene A, Hu B, Haas T, Plow E, Qin J. A structural mechanism of integrin alpha(IIb)beta(3) "inside-out" activation as regulated by its cytoplasmic face. Cell 2002; 110:587-97. [PMID: 12230976 DOI: 10.1016/s0092-8674(02)00906-6] [Citation(s) in RCA: 433] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Activation of the ligand binding function of integrin heterodimers requires transmission of an "inside-out" signal from their small intracellular segments to their large extracellular domains. The structure of the cytoplasmic domain of a prototypic integrin alpha(IIb)beta(3) has been solved by NMR and reveals multiple hydrophobic and electrostatic contacts within the membrane-proximal helices of its alpha and the beta cytoplasmic tails. The interface interactions are disrupted by point mutations or the cytoskeletal protein talin that are known to activate the receptor. These results provide a structural mechanism by which a handshake between the alpha and the beta cytoplasmic tails restrains the integrin in a resting state and unclasping of this interaction triggers the inside-out conformational signal that leads to receptor activation.
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50
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Kato A, Kawamata N, Tamayose K, Egashira M, Miura R, Fujimura T, Murayama K, Oshimi K. Ancient ubiquitous protein 1 binds to the conserved membrane-proximal sequence of the cytoplasmic tail of the integrin alpha subunits that plays a crucial role in the inside-out signaling of alpha IIbbeta 3. J Biol Chem 2002; 277:28934-41. [PMID: 12042322 DOI: 10.1074/jbc.m204340200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Modification of the cytoplasmic tails of the integrin alpha(IIb)beta(3) plays an important role in the signal transduction in platelets. We searched for proteins that bind to the alpha(IIb) cytoplasmic tail using the yeast two-hybrid assay with a cDNA library of the megakaryocyte-derived cell line and identified a protein, ancient ubiquitous protein 1 (Aup1), that is ubiquitously expressed in human cells. Observation of UT7/TPO cells expressing a red fluorescent protein-tagged Aup1 indicated its localization in the cytoplasm. Immunoprecipitation of UT7/TPO cells by an antibody for Aup1 revealed that approximately 40% of alpha(IIb) is complexed with Aup1. Binding study with an alpha(IIb) cytoplasmic tail peptide and glutathione S-transferase-Aup1 fusion protein revealed a low affinity (K(d) = 90 microm). Subsequent yeast two-hybrid assay indicated binding of Aup1 to cytoplasmic tails of other integrin alpha subunits. Binding study with the purified Aup1 and various glutathione S-transferase-alpha(IIb) cytoplasmic tail peptides revealed specific binding of Aup1 to the membrane-proximal sequence (KVGFFKR) that is conserved among the integrin alpha subunits and plays a crucial role in the alpha(IIb)beta(3) inside-out signaling. As Aup1 possesses domains related to signal transduction, these results suggest involvement of Aup1 in the integrin signaling.
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Affiliation(s)
- Atsushi Kato
- Division of Hematology, Department of Internal Medicine and Division of Biochemical Analysis, Central Laboratory of Medical Sciences, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
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